1. Field of the Invention
The present invention relates generally to a broadcast service method in a wireless data communication system, and in particular, to a method for providing a broadcast service to a mobile station over a packet data channel.
2. Description of the Related Art
The current communication environments are undergoing a sudden change without making any distinctions between wire/wireless areas and distinctions of regions and countries. In particular, such communication environment such as IMT-2000 (International Mobile Telecommunication 2000) tends to collectively provide information desired by a user as well as video and sound information on a real-time basis. In addition, with the development of mobile communication technology, the existing mobile communication systems enable a user to perform voice communication using a cellular phone and or a personal communications system (PCS) phone have evolved into advanced mobile communication systems capable of enabling a user not only to transmit text information but also to wirelessly view a broadcast service using a mobile station (MS).
In the broadcast service, a base station (BS) unidirectionally transmits high-rate forward data to a mobile station without reverse feedback information from the mobile station. In this regard the broadcast service is similar in concept to the general television broadcast service.
The current 3rd Generation Partnership Project 2 (3GPP2) is considering various service media and efficient resource utilization for a broadcast service in mobile communication systems. However, when the existing common channel is so designed to provide high broadcast service performance even at a cell boundary, cell capacity is excessively wasted. To compensate for this waste of capacity a CDMA2000 communication system, a 3rd generation mobile communication system, provides the broadcast service over a supplemental channel which is a dedicated channel proposed for a packet data service in order to reduce power consumption by a cell while to some extent securing the broadcast service performance.
For a broadcast service a supplemental channel uses a common long code mask instead of a dedicated long code mask. Performance of the supplemental channel, surpassing that of an existing common channel, is guaranteed by performing outer coding and autonomous handoff in which feedback information from a mobile station is not required during the broadcast service. In addition, the broadcast service prevents the mobile station from transmitting power control information and reverse feedback information, preventing a waste of cell capacity caused by a dedicated reverse channel. Theoretically, it is possible to accommodate an unlimited number of mobile stations within one cell.
Because the CDMA2000 communication system uses the outer coding technique instead of permitting retransmission even though there is a sufficient forward bandwidth for broadcasting data transmitted during the broadcast service, even a mobile station located at a cell boundary can obtain reception performance of a specific level with relatively lower power. However, when a radio channel condition instantaneously deteriorates in spite of the use of the outer coding technique, there is high possibility that the broadcasting data will be lost during transmission.
In order to meet users' demands for a mobile communication system capable of supporting a high-speed data service while supporting a voice service, a so-called 1×EVDV (Evolution Data and Voice) system has been proposed. The 1×EVDV system can transmit large amounts of data at high speed using a packet data channel (PDCH) capable of efficiently transmitting data compared to the existing supplemental channel.
The 1×EVDV system assigns all possible resources (spreading codes and power) to only one selected mobile station for a predetermined time period, using a dedicated identifier assigned to mobile stations receiving a data service. Upon failure to receive normal packet data for a time period assigned thereto, the mobile station transmits a non-Acknowledge signal (NAK) to a base station, and the base station repeatedly transmits the same packet data until an Acknowledge signal (ACK) is received from the mobile station.
However, when using the packet data channel as described above, the 1×EVDV system assigns a dedicated identifier to mobile stations so as to allow only a dedicated service, but does not support a service to be provided in common by all or some of mobile stations within a cell through the packet data channel. Although there is an identifier used to transmit system information to all mobile stations in the cell, because only one identifier is assigned to each cell, it cannot be used for a concurrent service for various broadcast contents and packet data.
Accordingly, there is a demand for a method capable of providing a more efficient broadcast service to mobile stations to enable them to receive a common service, using a forward packet data channel for a high-speed packet data service instead of a supplemental channel.